Multi-user transmission is a feature that involves transmitting data simultaneously to multiple intended recipient devices, for example, by aggregating frequency channels and using multiple-input multiple-output (MIMO) transmission techniques to spatially multiplex signals to the different recipient devices. For example, multi-user transmission techniques are employed in the IEEE 802.11ac very high throughput (VHT) amendment to the IEEE 802.11 wireless communication protocol. While multi-user transmissions significantly increase the throughput, they require conventional medium reservation techniques to be revisited.
One medium reservation technique is the request-to-send/clear-to-send (RTS/CTS) procedure. The purpose of the RTS/CTS exchange is to reserve the medium for the transmission by the initiator while giving protection to both the initiator and responder against any interfering transmissions initiated by other devices in the neighborhood of the initiator and responder. This is particularly important when there is overlap between Basic Service Sets of wireless access point devices in wireless local area networks (WLANs).